Actuators are, for example, known to be interposed between a vehicle body and a truck to suppress vibration in a lateral direction with respect to a traveling direction of the vehicle body of a railway vehicle.
Some of the above actuators are configured to include, for example, a cylinder, a piston slidably inserted into the cylinder, a rod inserted into the cylinder and coupled to the piston, a rod-side chamber and a piston-side chamber partitioned by the piston in the cylinder, a tank, a first on-off valve provided at an intermediate position of a first passage allowing communication between the rod-side chamber and the piston-side chamber, a second on-off valve provided at an intermediate position of a second passage allowing communication between the piston-side chamber and the tank, a pump for supplying liquid to the rod-side chamber, a motor for driving the pump, a discharge passage connecting the rod-side chamber to the tank and a variable relief valve provided at an intermediate position of the discharge passage.
For example, according to an actuator disclosed in JP2010-65797A, a direction of a thrust force to be output can be determined by appropriately opening and closing a first on-off valve and a second on-off valve. A thrust force of a desired magnitude can be output in a desired direction by adjusting a relief pressure of a variable relief valve to control a pressure in the cylinder while rotating a pump at a constant speed by a motor to supply at a constant flow rate into the cylinder.